The Friedel-Crafts Reaction: Acetylation of Ferrocene
Introduction:
This experiment is based on a reaction that was discovered in 1877 by Charles Friedel and James Crafts and are collectively known as Friedel-Crafts reactions. This experiment contains an electrophilic aromatic substitution reaction. In the reaction the electrophile replaces the hydrogen atom in an aromatic compound forming a new bond (carbon-carbon). The reaction bond formation allows the elaboration of simpler compounds into more complicated organic structures. Electrophilic aromatic substitution reactions characterize an electrophile replacing a hydrogen atom in an aromatic compound and formed a new carbon bond.In the experiment,we will explore the Friedel-Crafts acetylation of a cyclopentadienyl ring. Ferrocene, contains two cyclopentadienyl rings. Although the presence of the metal atom confers some unusual properties on ferrocene, the cyclopentadienyl rings undergo many reactions, typical of aromatic compounds. Ferrocene effectively experiences Friedel-Crafts acetylation. In this lab we will investigate the follow reaction:
Friedel-Crafts acylation of Ferrocene
*Discovery of new Friedel-Crafts-like reaction chemistry applicable to simple benzene derivatives remains an area of ongoing investigation.
Procedure:
Adapted from Doxsee, K. M.; Hutchison, J. E. Green Organic Chemistry: Strategies, Tools and Laboratory Experiments, First Edition, Brooks/Cole, 2004. pp. 244.
Tell me about the specific adaptations.
Data:
1. Round bottom flask contains 1.50g ferrocene sig figs, 5.0mL of acetic anhydride and 1.0 mL of 85% phosphoric acid.
As the reaction mixture warmed in the heated bath observations of a darken color change were observed. By the end of the steam bath the mixture's color was dark purplish.
Black purplish residue stuck to the bottom of the flask after the mixture was poured over 25g of ice.
2. The orange-brown mixture was stirred with a glass rod mixing the 25g of ice and 10mL of ice water.
3. 37.5 mL of 3M aqueous NaOH solution was added to the mixture.
4. The procedure called for the addition of 7-8g of sodium bicarbonate in small amounts until the mixture has been neutralized. It is important to
note the neutralization of the mixture was achieved with the addition of less than a gram of sodium bicarbonate.
5. After allowing the mixture to stand for 20 minutes, the mixture was place through vacuum filtration and dried.
6. The crude product was then collected. A small amount was set aside to conduct the TLC test. Due to the large crude product recovered (2.52g) sig figs
only a portion (.805g) was separate and used to continue the rest of the experiment.
7. 20mL of hexenes were added and heated gently in order to prevent the solvent from boiling off.
8. A spatula of decolorizing carbon was added and then hot filtration was performed, producing a reddish yet clear solution. Delicate reddish-orange crystals formed on the narrow portion of the hot filtration funnel that was exposed to the recovery flask. Tiny crystals also formed in the reddish solution as the flask was cooled in an ice bath.
9. A total of .073 grams crystals were recovered via vacuum filtration.
Name of Reactants
Mass
Molecular Formula
Molecular Mass
Number of Mols
Ferrocene
1.50g
C10H10Fe
186.03g/mol
0.0080 mols
Acetic Anhydride
1.08g/ml
C4H603
102.05g/mol
0.1060 mols
85% Phosphoric Acid
1.69g/ml
H3PO4
96.981g/mol
.01744 mols
Ferrocene+Acetic Anhydride
2.58g
Crude Product
2.52g
C12H12OFe
228.09g/mol
.00875 mols
% Yield of Crude Product .00875 % / .0080 % x 100 = 109 % reserve the use of the % label until the end.
Crude Product used to continue on with the experiment: .805g .805g / 228.09g/mol = .00352 mols
Final Product dry crystals: .073g / 228.07g of acetylferrocene =.00025 mols
% Recovery acetylferrocene .00025 mol / portion of crude product .00352 x 100 = 7 %
Melting Points
Final products melting point 84.2 C and a color change from red to clear. always report melting point RANGES.
Reported melting point for recrystallized acetylferrocene is 82-83 C or 84-85 C
TLC Test
Column F: Pure ferrocene traveled 46 cm up the TLC paper. The line was yellow
Column CP: Crude product traveled 10cm up the TLC paper, the spot was orange. A thin yellow line appeared at 46 cm. This yellow line indicates the presence of unreacted ferrocene.
Column FP: Final product (Acetylferrocene) traveled 8cm up the TLC paper, the spot was orange. A very small, faint hue of yellow appeared at 46 cm indicating a residual amount of unreacted ferrocene remained in the final product.
Conclusion:
The steps completed after the crude product was collected, including hot filtration and vacuum filtration, eliminated the majority of the original ferrocene and any other impurities. The color change in the crude and final products shown in the TLC indicates that chemical reactions had occurred as desired. The lack of yellow at the 46cm mark of the final product combined with the melt point being at 84.2 C confirms that the experiment was successful with very little unreacted ferrocene or other contaminants in the final acetylferrocene product.
2 additional Friedel-Crafts Acylation reactions
Mild, Efficient Friedel-Crafts Acylations from Carboxylic Acids Using Cyanuric Chloride and AlCl3 Cyrous O. Kangani* and Billy W. Day *Department of Medicine, School of Medicine, and Departments of Pharmaceutical Sciences and of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, Email: cyrouskangani
http://www.organic-chemistry.org/at.gif
gmail.com C. O. Kangani, B. W. Day, Org. Lett., 2008, 10, 2645-264
Friedel–Crafts acylation
Friedel–Crafts acylation is the acylation of aromatic rings with an acyl chloride using a strong Lewis acid catalyst. Friedel–Crafts acylation is also possible with acid anhydrides. Reaction conditions are similar to the Friedel–Crafts alkylation mentioned above. This reaction has several advantages over the alkylation reaction. Due to the electron-withdrawing effect of the carbonyl group, the ketone product is always less reactive than the original molecule, so multiple acylations do not occur. Also, there are no carbocation rearrangements, as the carbonium ion is stabilized by a resonance structure in which the positive charge is on the oxygen.
Friedel–Crafts acylation overview
The viability of the Friedel–Crafts acylation depends on the stability of the acyl chloride reagent. Formyl chloride, for example, is too unstable to be isolated. Thus, synthesis of benzaldehyde via the Friedel–Crafts pathway requires that formyl chloride be synthesized in situ. This is accomplished via the Gattermann-Koch reaction, accomplished by reacting benzene with carbon monoxide and hydrogen chloride under high pressure, catalyzed by a mixture of aluminium chloride and cuprous chloride. http://en.wikipedia.org/wiki/Friedel%E2%80%93Crafts_reaction accessed February 25, 2011.
The Friedel-Crafts Reaction: Acetylation of Ferrocene
Introduction:
This experiment is based on a reaction that was discovered in 1877 by Charles Friedel and James Crafts and are collectively known as Friedel-Crafts reactions. This experiment contains an electrophilic aromatic substitution reaction. In the reaction the electrophile replaces the hydrogen atom in an aromatic compound forming a new bond (carbon-carbon). The reaction bond formation allows the elaboration of simpler compounds into more complicated organic structures. Electrophilic aromatic substitution reactions characterize an electrophile replacing a hydrogen atom in an aromatic compound and formed a new carbon bond.In the experiment,we will explore the Friedel-Crafts acetylation of a cyclopentadienyl ring. Ferrocene, contains two cyclopentadienyl rings. Although the presence of the metal atom confers some unusual properties on ferrocene, the cyclopentadienyl rings undergo many reactions, typical of aromatic compounds. Ferrocene effectively experiences Friedel-Crafts acetylation. In this lab we will investigate the follow reaction:
*Discovery of new Friedel-Crafts-like reaction chemistry applicable to simple benzene derivatives remains an area of ongoing investigation.
Procedure:
Adapted from Doxsee, K. M.; Hutchison, J. E. Green Organic Chemistry: Strategies, Tools and Laboratory Experiments, First Edition, Brooks/Cole, 2004. pp. 244.
Tell me about the specific adaptations.
Data:
1. Round bottom flask contains 1.50g ferrocene sig figs, 5.0mL of acetic anhydride and 1.0 mL of 85% phosphoric acid.
As the reaction mixture warmed in the heated bath observations of a darken color change were observed. By the end of the steam bath the mixture's color was dark purplish.
Black purplish residue stuck to the bottom of the flask after the mixture was poured over 25g of ice.
2. The orange-brown mixture was stirred with a glass rod mixing the 25g of ice and 10mL of ice water.
3. 37.5 mL of 3M aqueous NaOH solution was added to the mixture.
4. The procedure called for the addition of 7-8g of sodium bicarbonate in small amounts until the mixture has been neutralized. It is important to
note the neutralization of the mixture was achieved with the addition of less than a gram of sodium bicarbonate.
5. After allowing the mixture to stand for 20 minutes, the mixture was place through vacuum filtration and dried.
6. The crude product was then collected. A small amount was set aside to conduct the TLC test. Due to the large crude product recovered (2.52g) sig figs
only a portion (.805g) was separate and used to continue the rest of the experiment.
7. 20mL of hexenes were added and heated gently in order to prevent the solvent from boiling off.
8. A spatula of decolorizing carbon was added and then hot filtration was performed, producing a reddish yet clear solution. Delicate reddish-orange crystals formed on the narrow portion of the hot filtration funnel that was exposed to the recovery flask. Tiny crystals also formed in the reddish solution as the flask was cooled in an ice bath.
9. A total of .073 grams crystals were recovered via vacuum filtration.
% Yield of Crude Product .00875 % / .0080 % x 100 = 109 %
reserve the use of the % label until the end.
Crude Product used to continue on with the experiment: .805g .805g / 228.09g/mol = .00352 mols
Final Product dry crystals: .073g / 228.07g of acetylferrocene =.00025 mols
% Recovery acetylferrocene .00025 mol / portion of crude product .00352 x 100 = 7 %
Melting Points
Final products melting point 84.2 C and a color change from red to clear. always report melting point RANGES.
Reported melting point for recrystallized acetylferrocene is 82-83 C or 84-85 C
TLC Test
Column F: Pure ferrocene traveled 46 cm up the TLC paper. The line was yellow
Column CP: Crude product traveled 10cm up the TLC paper, the spot was orange. A thin yellow line appeared at 46 cm. This yellow line indicates the presence of unreacted ferrocene.
Column FP: Final product (Acetylferrocene) traveled 8cm up the TLC paper, the spot was orange. A very small, faint hue of yellow appeared at 46 cm indicating a residual amount of unreacted ferrocene remained in the final product.
Conclusion:
The steps completed after the crude product was collected, including hot filtration and vacuum filtration, eliminated the majority of the original ferrocene and any other impurities. The color change in the crude and final products shown in the TLC indicates that chemical reactions had occurred as desired. The lack of yellow at the 46cm mark of the final product combined with the melt point being at 84.2 C confirms that the experiment was successful with very little unreacted ferrocene or other contaminants in the final acetylferrocene product.
2 additional Friedel-Crafts Acylation reactions
Mild, Efficient Friedel-Crafts Acylations from Carboxylic Acids Using Cyanuric Chloride and AlCl3
Cyrous O. Kangani* and Billy W. Day
*Department of Medicine, School of Medicine, and Departments of Pharmaceutical Sciences and of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, Email: cyrouskangani
C. O. Kangani, B. W. Day, Org. Lett., 2008, 10, 2645-264
Friedel–Crafts acylation
Friedel–Crafts acylation is the acylation of aromatic rings with an acyl chloride using a strong Lewis acid catalyst. Friedel–Crafts acylation is also possible with acid anhydrides. Reaction conditions are similar to the Friedel–Crafts alkylation mentioned above. This reaction has several advantages over the alkylation reaction. Due to the electron-withdrawing effect of the carbonyl group, the ketone product is always less reactive than the original molecule, so multiple acylations do not occur. Also, there are no carbocation rearrangements, as the carbonium ion is stabilized by a resonance structure in which the positive charge is on the oxygen.
The viability of the Friedel–Crafts acylation depends on the stability of the acyl chloride reagent. Formyl chloride, for example, is too unstable to be isolated. Thus, synthesis of benzaldehyde via the Friedel–Crafts pathway requires that formyl chloride be synthesized in situ. This is accomplished via the Gattermann-Koch reaction, accomplished by reacting benzene with carbon monoxide and hydrogen chloride under high pressure, catalyzed by a mixture of aluminium chloride and cuprous chloride.
http://en.wikipedia.org/wiki/Friedel%E2%80%93Crafts_reaction accessed February 25, 2011.